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Paper: He II Raman Scattering in the Young Planetary Nebula IC 5117
Volume: 362, The Seventh Pacific Rim Conference on Stellar Astrophysics
Page: 216
Authors: Lee, H.-W.; Jung, Y.-C.; Song, I.-O.
Abstract: Substantial mass loss is an essential part of late stages of stellar evolution. It is believed that a young planetary nebula is surrounded by a thick neutral region, which is illuminated by strong UV radiation emanating from the central hot star evolving into a white dwarf. In this circumstance, it is expected that UV radiation is Raman scattered by atomic hydrogen to be redistributed into other spectral regions including the optical and infrared. In particular, the scattering cross section is very large near Lyman series resonances and hence He II lines can be easily Raman scattered to form scattered features blueward of H I Balmer series lines. We present our spectrum of the young planetary nebula IC 5117 that exhibits Raman-scattered features around 6545 and 4850, blueward of Hβ and Hβ, respectively. We compute the Raman conversion efficiency and conclude that this young planetary nebula is almost completely surrounded by a thick neutral region with H I column density exceeding 1021 cm−2.
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